~ Collection of Interview Questions

Binary Search

/*
* The MIT License
*
* Copyright 2012 Abhijit Gaikwad <gaikwad.abhijit@gmail.com>.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/**
*
* @author Abhijit Gaikwad <gaikwad.abhijit@gmail.com> visit http://gabhi.com
*/
package com.gabhi.search;
/**
*
* @author Abhijit Gaikwad <gaikwad.abhijit@gmail.com>
*/
//Implement Binary Search
/**
* A straightforward implementation of binary search is recursive. The initial
* call uses the indices of the entire array to be searched. The procedure then
* calculates an index midway between the two indices, determines which of the
* two subarrays to search, and then does a recursive call to search that
* subarray. Each of the calls is tail recursive, so a compiler need not make a
* new stack frame for each call. The variables imin and imax are the lowest and
* highest inclusive indices that are searched.
*
*/
public class BinarySearch {
public static final int NOT_FOUND = -1;
public static void main(String[] args) {
int SIZE = 8;
Comparable[] a = new Integer[SIZE];
for (int i = 0; i < SIZE; i++) {
a[ i] = new Integer(i * 2);
}
for (int i = 0; i < SIZE * 2; i++) {
System.out.println("Found " + i + " at "
+ binarySearch(a, new Integer(i)));
}
}
public static int binarySearch(Comparable[] a, Comparable x) {
int low = 0;
int high = a.length - 1;
int mid;
while (low <= high) {
mid = (low + high) / 2;
if (a[ mid].compareTo(x) < 0) {
low = mid + 1;
} else if (a[ mid].compareTo(x) > 0) {
high = mid - 1;
} else {
return mid;
}
}
return NOT_FOUND; // NOT_FOUND = -1
}
}